PGC1α protects against hepatic steatosis and insulin resistance via enhancing IL10-mediated anti-inflammatory response

Reduced liver mitochondrial energy metabolism impairs food intake regulation following gastric preloads and fasting

OBJECTIVE

The capacity of the liver to serve as a peripheral sensor in the regulation of food intake has been debated for over half a century. The anatomical position and physiological roles of the liver suggest it is a prime candidate to serve as an interoceptive sensor of peripheral tissue and systemic energy state. Importantly, maintenance of liver ATP levels and within-meal food intake inhibition is impaired in human subjects with obesity and obese pre-clinical models. Previously, we have shown decreased hepatic mitochondrial energy metabolism (i.e., oxidative metabolism & ADP-dependent respiration) in male liver-specific, heterozygous PGC1a mice results in increased short-term diet-induced weight gain with increased within meal food intake. Herein, we tested the hypothesis that decreased liver mitochondrial energy metabolism impairs meal termination following nutrient oral pre-loads.

METHODS

Liver mitochondrial respiratory response to changes in ΔGATP and adenine nucleotide concentration following fasting were examined in male liver-specific, heterozygous PGC1a mice. Further, food intake and feeding behavior during basal conditions, following nutrient oral pre-loads, and following fasting were investigated.

RESULTS

We observed male liver-specific, heterozygous PGC1a mice have reduced mitochondrial response to changes in ΔGATP and tissue ATP following fasting. These impairments in liver energy state are associated with larger and longer meals during chow feeding, impaired dose-dependent food intake inhibition in response to mixed and individual nutrient oral pre-loads, and greater acute fasting-induced food intake.

CONCLUSIONS

These data support previous work proposing liver-mediated food intake regulation through modulation of peripheral satiation signals.

The PPAR-α agonist oleoyethanolamide (OEA) ameliorates valproic acid-induced steatohepatitis in rats via suppressing Wnt3a/β-catenin and activating PGC-1α: Involvement of network pharmacology and molecular docking

Liver damage is one of the most severe side effects of valproic acid (VPA) therapy. Research indicates that PPAR-α prevents Wnt3a/β-catenin-induced PGC-1α dysregulation, which is linked to liver injury. Although PPAR-α activation has hepatoprotective effects, its role in preventing VPA-induced liver injury remains unclear. Our research used network analysis, molecular docking, and in-vivo validation to predict and assess targets and pathways associated with the hepatoprotective effects of oleoylethanolamide (OEA), a PPAR-α agonist, on VPA-induced steatohepatitis. For in-vivo experiments, 24 rats were assigned to V, OEA, VPA, and OEA + VPA. Liver functions, TGs, cholesterol, and LDL were tested. Hepatic levels of PPAR-α, ACO, TNF-α, IL-1β, HO-1, MDA, and TAC, along with Wnt3a/β-catenin, PGC-1α, and Nrf2 expression were assessed. Further, NF-κB, Bax, Bcl-2, and caspase-3 expression were detected immunohistochemically. Network pharmacology identified 258 targets for OEA-steatohepatitis connection, including NFKB1, PPARA, and NFE2L2, in addition to TNF, non-alcoholic fatty liver, NF-κB, PPAR, and WNT signaling, as contributing to steatohepatitis pathogenesis. The docking revealed a strong affinity between OEA and Wnt3a, β-catenin, and PGC-1α. Therefore, we postulated that the hepatoprotective effect of OEA may be due to Wnt3a/β-catenin-mediated inactivation of PGC1-α pathway. In vivo, OEA inhibited Wnt3a/β-catenin and increased PGC1-α by activating PPAR-α. Hence, PGC1-α reduced fat cell β-oxidation and NF-κB-mediated inflammation. OEA lessened MDA and raised TAC to mitigate oxidative damage. OEA additionally reduced apoptosis by lowering Bax/Bcl-2 ratio and caspase-3. In summary, PPAR-α involvement in the protective effects of OEA against VPA-induced steatohepatitis can be confirmed by suppressing Wnt3a/β-catenin and activating PGC-1α signaling.

GTPBP8 mitigates nonalcoholic steatohepatitis (NASH) by depressing hepatic oxidative stress and mitochondrial dysfunction via PGC-1α signaling

Nonalcoholic steatohepatitis (NASH) is emerging as a major cause of liver transplantation and hepatocellular carcinoma (HCC). Regrettably, its pathological mechanisms are still not fully comprehended. GTP-binding protein 8 (GTPBP8), belonging to the GTP-binding protein superfamily, assumes a crucial role in RNA metabolism, cell proliferation, differentiation, and signal transduction. Its aberrant expression is associated with oxidative stress and mitochondrial dysfunctions. Nevertheless, its specific functions and mechanisms of action, particularly in NASH, remain elusive. In our current study, we initially discovered that human hepatocytes L02 displayed evident mitochondrial respiratory anomaly, mitochondrial damage, and dysfunction upon treatment with palmitic acids and oleic acids (PO), accompanied by significantly reduced GTPBP8 expression levels through RNA-Seq, RT-qPCR, western blotting, and immunofluorescence assays. We then demonstrated that GTPBP8 overexpression mediated by adenovirus vector (Ad-GTPBP8) markedly attenuate lipid accumulation, inflammatory response, and mitochondrial impair and dysfunction in hepatocytes stimulated by PO. Conversely, adenovirus vector-mediated GTPBP8 knockdown (Ad-shGTPBP8) significantly accelerated lipid deposition, inflammation and mitochondrial damage in PO-treated hepatocytes in vitro. Furthermore, we constructed an in vivo NASH murine model by giving a 16-week high fat high cholesterol diet (HFHC) diet to hepatocyte specific GTPBP8-knockout (GTPBP8HKO) mice. We firstly found that HFHC feeding led to metabolic disorder in mice, including high body weight, blood glucose and insulin levels, and liver dysfunctions, which were accelerated in these NASH mice with GTPBP8 deficiency in hepatocytes. Consistently, GTPBP8HKO remarkably exacerbated the progression of NASH phenotypes induced by HFHC, as proved by the anabatic lipid accumulation, inflammation, fibrosis and reactive oxygen species (ROS) production in liver tissues, which could be largely attributed to the severe mitochondrial damage and dysfunction. Mechanistically, we further identified that GTPBP8 interacted with peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) in hepatocytes. Importantly, the hepaprotective effects of GTPBP8 against mitochondrial dysfunction, oxidative stress and inflammation was largely dependent on PGC-1α expression. Collectively, GTPBP8 may exert a protective role in the progression of NASH, and targeting the GTPBP8/PGC-1α axis may represent a potential strategy for NASH treatment by improving mitochondrial functions.

Reduced Liver Mitochondrial Energy Metabolism Impairs Food Intake Regulation Following Gastric Preloads and Fasting

Objective

The capacity of the liver to serve as a peripheral sensor in the regulation of food intake has been debated for over half a century. The anatomical position and physiological roles of the liver suggest it is a prime candidate to serve as an interoceptive sensor of peripheral tissue and systemic energy state. Importantly, maintenance of liver ATP levels and within-meal food intake inhibition is impaired in human subjects with obesity and obese pre-clinical models. Previously, we have shown decreased hepatic mitochondrial energy metabolism (i.e., oxidative metabolism & ADP-dependent respiration) in male liver-specific, heterozygous PGC1a mice results in increased short-term diet-induced weight gain with increased within meal food intake. Herein, we tested the hypothesis that decreased liver mitochondrial energy metabolism impairs meal termination following nutrient oral pre-loads.

Methods

Liver mitochondrial respiratory response to changes in ΔGATP and adenine nucleotide concentration following fasting were examined in male liver-specific, heterozygous PGC1a mice. Further, food intake and feeding behavior during basal conditions, following nutrient oral pre-loads, and following fasting were investigated.

Results

We observed male liver-specific, heterozygous PGC1a mice have reduced mitochondrial response to changes in ΔGATP and tissue ATP following fasting. These impairments in liver energy state are associated with larger and longer meals during chow feeding, impaired dose-dependent food intake inhibition in response to mixed and individual nutrient oral pre-loads, and greater acute fasting-induced food intake.

Conclusion

These data support previous work proposing liver-mediated food intake regulation through modulation of peripheral satiation signals.

Dietary caloric input and tumor growth accelerate senescence and modulate liver and adipose tissue crosstalk

Metabolic alterations are related to tumorigenesis and other age-related diseases that are accelerated by "Westernized" diets. In fact, hypercaloric nutrition is associated with an increased incidence of cancers and faster aging. Conversely, lifespan-extending strategies, such as caloric restriction, impose beneficial effects on both processes. Here, we investigated the metabolic consequences of hypercaloric-induced aging on tumor growth in female mice. Our findings indicate that a high-fat high-sucrose diet increases tumor growth mainly due to the boosted oxidation of glucose and fatty acids. Consequently, through an increased expression of lactate, IGFBP3, and PTHLH, tumors modulate liver and white adipose tissue metabolism. In the liver, the induced tumor increases fibrosis and accelerates the senescence process, despite the lower systemic pro-inflammatory state. Importantly, the induced tumor induces the wasting and browning of white adipose tissue, thereby reversing diet-induced insulin resistance. Finally, we suggest that tumor growth alters liver-adipose tissue crosstalk that upregulates Fgf21, induces senescence, and negatively modulates lipids and carbohydrates metabolism even in caloric-restricted-fed mice.

Chiglitazar attenuates high-fat diet-induced nonalcoholic fatty liver disease by modulating multiple pathways in mice

Nonalcoholic fatty liver disease (NAFLD) is one of the most common chronic liver diseases worldwide; however, effective intervention strategies for NAFLD are still unavailable. The present study sought to investigate the efficacy of chiglitazar, a pan-PPAR agonist, in protecting against NAFLD in mice and its underlying molecular mechanism. Male C57BL/6 J mice were fed a high-fat diet (HFD) for 8 weeks to generate NAFLD and the HFD was continued for an additional 10 weeks in the absence or presence of 5 mg/kg/d or 10 mg/kg/d chiglitazar by gavage. Chiglitazar significantly improved dyslipidemia and insulin resistance, ameliorated hepatic steatosis and reduced liver inflammation and oxidative stress in NAFLD mice. RNA-seq revealed that chiglitazar alleviated HFD-induced NAFLD in mice through multiple pathways, including fatty acid metabolism regulation, insulin signaling pathway, and AMPK signaling pathway. This study demonstrated the potential therapeutic effect of chiglitazar on NAFLD. Chiglitazar ameliorated NAFLD by modulating multiple pathways.

Hepatic-specific Pgc-1α ablation drives fibrosis in a MASH model

BACKGROUND & AIMS

Metabolic dysfunction-associated steatohepatitis (MASH) is a growing cause of chronic liver disease, characterized by fat accumulation, inflammation and fibrosis, which development depends on mitochondrial dysfunction and oxidative stress. Highly expressed in the liver during fasting, peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) regulates mitochondrial and oxidative metabolism. Given the relevant role of mitochondrial function in MASH, we investigated the relationship between PGC-1α and steatohepatitis.

METHODS

We measured the hepatic expression of Pgc-1α in both MASH patients and wild-type mice fed a western diet (WD) inducing steatosis and fibrosis. We then generated a pure C57BL6/J strain loss of function mouse model in which Pgc-1α is selectively deleted in the liver and we fed these mice with a WD supplemented with sugar water that accurately mimics human MASH.

RESULTS

We observed that the hepatic expression of Pgc-1α is strongly reduced in MASH, in both humans and mice. Moreover, the hepatic ablation of Pgc-1α promotes a considerable reduction of the hepatic mitochondrial respiratory capacity, setting up a bioenergetic harmful environment for liver diseases. Indeed, the lack of Pgc-1α decreases mitochondrial function and increases inflammation, fibrosis and oxidative stress in the scenario of MASH. Intriguingly, this profibrotic phenotype is not linked with obesity, insulin resistance and lipid disbalance.

CONCLUSIONS

In a MASH model the hepatic ablation of Pgc-1α drives fibrosis independently from lipid and glucose metabolism. These results add a novel mechanistic piece to the puzzle of the specific and crucial role of mitochondrial function in MASH development.

From metabolism to malignancy: the multifaceted role of PGC1α in cancer

PGC1α, a central player in mitochondrial biology, holds a complex role in the metabolic shifts seen in cancer cells. While its dysregulation is common across major cancers, its impact varies. In some cases, downregulation promotes aerobic glycolysis and progression, whereas in others, overexpression escalates respiration and aggression. PGC1α's interactions with distinct signaling pathways and transcription factors further diversify its roles, often in a tissue-specific manner. Understanding these multifaceted functions could unlock innovative therapeutic strategies. However, challenges exist in managing the metabolic adaptability of cancer cells and refining PGC1α-targeted approaches. This review aims to collate and present the current knowledge on the expression patterns, regulators, binding partners, and roles of PGC1α in diverse cancers. We examined PGC1α's tissue-specific functions and elucidated its dual nature as both a potential tumor suppressor and an oncogenic collaborator. In cancers where PGC1α is tumor-suppressive, reinstating its levels could halt cell proliferation and invasion, and make the cells more receptive to chemotherapy. In cancers where the opposite is true, halting PGC1α's upregulation can be beneficial as it promotes oxidative phosphorylation, allows cancer cells to adapt to stress, and promotes a more aggressive cancer phenotype. Thus, to target PGC1α effectively, understanding its nuanced role in each cancer subtype is indispensable. This can pave the way for significant strides in the field of oncology.

An Ilex latifolia‐containing compound tea regulates glucose–lipid metabolism and modulates gut microbiota in high‐fat diet‐fed mice

Kuding Tea (Ilex latifolia) is a bitter‐tasting herbal tea that was used for the treatment of symptoms related with diabetes mellitus, hypertension, and hyperlipidemia. However, Kuding Tea is also difficultly accepted by people in daily life because of its poor palatability. In this study, Kuding Tea, green tea (GT) (Camellia sinensis L.), and Luohan (Siraitia grosvenorii) fruits were formulated into a compound Kuding Tea (CKT) to improve the taste and health benefits of this beverage. High‐fat diet‐fed male C57BL/6J mice were used as animal models to explore the effects of CKT (6 or 12 mg/mL, water ad libitum) on body weight, food intake, liver function, blood glucose and lipids, and gene expression. L02 and 3T3‐L1 cells were used to further demonstrate the effects of CKT on fat accumulation and hepatic lipid deposition. Our results suggest that CKT can regulate glucose and lipid metabolism by decreasing body weight, reducing white adipose deposition, improving glucose tolerance, increasing the expression of brown adipose genes, and reducing fat accumulation in the liver, and CKT inhibited fat accumulation better than GT. In addition, a low dose (6 mg/mL) of CKT reduced the abundance of Desulfovibrio bacteria, positively associated with obesity, and increased that of norank_f__Muribaculaceae, Lachnospiraceae_NK4A136_group, and Alloprevotella, which are beneficial to glucose and lipid metabolism. This study suggests that CKT not only has a better palatability but also has potential preventive effects on high‐fat diet‐induced glucose–lipid metabolic diseases.

Mucosal Genes Encoding Clock, Inflammation and Their Mutual Regulators Are Disrupted in Pediatric Patients with Active Ulcerative Colitis

Patients with active ulcerative colitis (UC) display a misalignment of the circadian clock, which plays a vital role in various immune functions. Our aim was to characterize the expression of clock and inflammation genes, and their mutual regulatory genes in treatment-naïve pediatric patients with UC. Using the Inflammatory Bowel Disease Transcriptome and Metatranscriptome Meta-Analysis (IBD TaMMA) platform and R algorithms, we analyzed rectal biopsy transcriptomic data from two cohorts (206 patients with UC vs. 20 healthy controls from the GSE-109142 study, and 43 patients with UC vs. 55 healthy controls from the GSE-117993 study). We compared gene expression levels and correlation of clock genes (BMAL1, CLOCK, PER1, PER2, CRY1, CRY2), inflammatory genes (IκB, IL10, NFκB1, NFκB2, IL6, TNFα) and their mutual regulatory genes (RORα, RORγ, REV-ERBα, PGC1α, PPARα, PPARγ, AMPK, SIRT1) in patients with active UC and healthy controls. The clock genes BMAL1, CLOCK, PER1 and CRY1 and the inflammatory genes IκB, IL10, NFκB1, NFκB2, IL6 and TNFα were significantly upregulated in patients with active UC. The genes encoding the mutual regulators RORα, RORγ, PGC1α, PPARα and PPARγ were significantly downregulated in patients with UC. A uniform pattern of gene expression was found in healthy controls compared to the highly variable expression pattern in patients with UC. Among the healthy controls, inflammatory genes were positively correlated with clock genes and they all showed reduced expression. The difference in gene expression levels was associated with disease severity and endoscopic score but not with histological score. In patients with active UC, clock gene disruption is associated with abnormal mucosal immune response. Disrupted expression of genes encoding clock, inflammation and their mutual regulators together may play a role in active UC.

PGC1α deficiency reverses cholestasis-induced liver injury via attenuating hepatic inflammation and promoting bile duct remodeling

OBJECTIVES

Cholestatic liver diseases are characterized by hepatocellular damage, cholangiocyte proliferation, and progressive fibrosis. Bile duct ligation (BDL) is widely used to resemble liver injuries induced by cholestasis. Peroxisome proliferator-activated receptor-gamma coactivator 1 alpha (PGC1α) was reported to play a critical role in multiple biological responses. Nevertheless, whether PGC1α is involved in bile acid metabolism and biliary disorders remains unclear. This study aimed to investigate the effect of PGC1α on hepatic responses after cholestatic injury.

MATERIALS AND METHODS

Wild-type mice were subjected to BDL or sham surgery for 14 days and human liver specimens from patients with primary biliary cholangitis (PBC) were collected to detect the expression of PGC1α. Hepatic-specific PGC1α knockout mice (HKO) were constructed and subjected to BDL, in which the effects of PGC1α on cholestatic liver injury were demonstrated by biochemical and histopathological assessments, immunoblotting, and metabolomics.

RESULTS

The expression of PGC1α was upregulated in the liver of PBC patients and murine models. Both in vivo and in vitro experiments supported the protective effects of PGC1α on cholestasis-induced hepatocyte injury. Infiltrated inflammatory cells after BDL were decreased in HKO mice. Inhibited Wnt/β-Catenin pathway and enhanced Notch signaling promoted transdifferentiation of hepatic progenitor cells (HPC)/ hepatocytes into cholangiocytes, leading to the greater ductular reaction observed in the HKO mice. But bile acids metabolism and mitochondrial function were not affected due to hepatic PGC1α deficiency in cholestasis.

CONCLUSIONS

Hepatic-specific deletion of PGC1α regulated liver regeneration by promoting ductular reactions, thereby exerting protective effects against BDL-induced liver injury, which could be a new potential therapeutic target.

A low-carbohydrate diet with different fatty acids' sources in the treatment of obesity: Impact on insulin resistance and adipogenesis

BACKGROUND

The search for nutritional intervention strategies against obesity has grown, highlighting the low-carbohydrate diet model. However, little is known about the impact of the quality of fatty acids consumed in this diet. Thus, we aim to investigate the influence of fatty acid quality on dietary strategy on obesity.

METHODS

Male Swiss mice were diet-induced to obesity. Afterward, mice consume a low-carb diet with different types of fat: saturated, polyunsaturated ω-3, ω-6, and monounsaturated ω-9 fatty acids. Weight gain and food consumption were monitored weekly. An oral glucose tolerance test was performed and blood and tissue samples were collected for analysis of insulin resistance markers. Protein expression of insulin signaling pathway molecules, lipid metabolism, mitochondrial function, macrophage polarization, and cytokine production were analyzed.

RESULTS

The high-fat diet was able to induce obesity and glucose intolerance. The switch to a low-carbohydrate dietary pattern reversed the glucose intolerance, with better results in the ω-3 and ω-9 groups. After the low-carbohydrate diet, groups ω-3 and ω-9 presented improved fasting serum glucose, insulin, and HOMA indexes. The low-carbohydrate diet also increased the activity of insulin pathway proteins such as IR, IRS1, and AKT. Furthermore, the ω-3 diet group showed greater activity of mitochondrial complexes and AMPK signaling pathway proteins. The ω-6 and ω-9 -rich diet induced M2-type macrophage polarization, as well as cytokine production modulation by the low-carbohydrate diet in the ω-3 and ω-9 groups.

CONCLUSIONS

Consuming a low-carbohydrate diet pattern promotes weight loss and improves glucose intolerance in obesity. Also, the quality of lipids has a direct influence, demonstrating that the consumption of ω-3 polyunsaturated and ω-9 monounsaturated lipids can lead to more favorable outcomes for the improvement of glucose intolerance, lipid metabolism, and anti-inflammatory effects.

A high fat, high sugar diet induces hepatic Peroxisome proliferator-activated receptor gamma coactivator 1-alpha promoter hypermethylation in male Wistar rats

Previously we reported that a high fat, high sugar (HFHS) diet induced adiposity, hyperinsulinaemia, hyperleptinaemia, hypertriglyceridaemia and increased liver mass in male Wistar rats. In the present study, the mechanisms underlying the increased liver mass were further elucidated by assessing hepatic lipid accumulation and the expression and methylation status of key metabolic genes using histology, quantitative real-time PCR and pyrosequencing, respectively. The HFHS diet induced hepatic steatosis, increased hepatic triglycerides (1.8-fold, p < 0.001), and increased the expression of sterol regulatory element-binding transcription factor 1 (Srebf1) (2.0-fold, p < 0.001) and peroxisome proliferator-activated receptor gamma (Pparg) (1.7-fold, p = 0.017) in the liver. The expression of peroxisome proliferator-activated receptor gamma coactivator 1 alpha (Pgc1a) was decreased (2.6-fold, p < 0.010), which was accompanied by hypermethylation (p = 0.018) of a conserved CpG site in the promoter of Pgc1a in HFHS fed rats compared to controls. In silico analysis identified putative binding sites for CCAAT/enhancer-binding protein beta (C/EBPß) and hepatocyte nuclear factor 1 (HNF1) within proximity to the hypermethylated CpG. As Pgc1a is a co-activator of several transcription factors regulating multiple metabolic pathways, hypermethylation of this conserved CpG site in the promoter of Pgc1a may be one possible mechanism contributing to the development of hepatic steatosis in response to a HFHS diet. However, further work is required to confirm the role of Pgc1a in steatosis.

Mitochondrial Dysfunction-Associated Mechanisms in the Development of Chronic Liver Diseases

The liver is a major metabolic organ that performs many essential biological functions such as detoxification and the synthesis of proteins and biochemicals necessary for digestion and growth. Any disruption in normal liver function can lead to the development of more severe liver disorders. Overall, about 3 million Americans have some type of liver disease and 5.5 million people have progressive liver disease or cirrhosis, in which scar tissue replaces the healthy liver tissue. An estimated 20% to 30% of adults have excess fat in their livers, a condition called steatosis. The most common etiologies for steatosis development are (1) high caloric intake that causes non-alcoholic fatty liver disease (NAFLD) and (2) excessive alcohol consumption, which results in alcohol-associated liver disease (ALD). NAFLD is now termed "metabolic-dysfunction-associated steatotic liver disease" (MASLD), which reflects its association with the metabolic syndrome and conditions including diabetes, high blood pressure, high cholesterol and obesity. ALD represents a spectrum of liver injury that ranges from hepatic steatosis to more advanced liver pathologies, including alcoholic hepatitis (AH), alcohol-associated cirrhosis (AC) and acute AH, presenting as acute-on-chronic liver failure. The predominant liver cells, hepatocytes, comprise more than 70% of the total liver mass in human adults and are the basic metabolic cells. Mitochondria are intracellular organelles that are the principal sources of energy in hepatocytes and play a major role in oxidative metabolism and sustaining liver cell energy needs. In addition to regulating cellular energy homeostasis, mitochondria perform other key physiologic and metabolic activities, including ion homeostasis, reactive oxygen species (ROS) generation, redox signaling and participation in cell injury/death. Here, we discuss the main mechanism of mitochondrial dysfunction in chronic liver disease and some treatment strategies available for targeting mitochondria.

Zinc Improves Semen Parameters in High-Fat Diet-Induced Male Rats by Regulating the Expression of LncRNA in Testis Tissue

This study aimed to identify differentially expressed LncRNAs in testis tissue of male rats induced by high-fat diet and their changes after zinc supplementation, by constructing a high-fat feeding rat model, and then supplemented with zinc, and observed the expression of LncRNA in three groups of normal, high-fat fed, and zinc-intervened rats. Experimental studies show that the semen parameters of male rats with high-fat diet were decreased but recovered after zinc supplementation, and the related LncRNA also changed. Zinc may improve the high-fat diet-induced reduction of semen parameters by changing the expression of related LncRNA.

Maternal hepatic adaptations during obese pregnancy encompass lobe-specific mitochondrial alterations and oxidative stress

Maternal obesity (MO) is rising worldwide, affecting half of all gestations, constituting a possible risk-factor for some pregnancy-associated liver diseases (PALD) and hepatic diseases. PALD occur in approximately 3% of pregnancies and are characterized by maternal hepatic oxidative stress (OS) and mitochondrial dysfunction. Maternal hepatic disease increases maternal and fetal morbidity and mortality. Understanding the role of MO on liver function and pathophysiology could be crucial for better understanding the altered pathways leading to PALD and liver disease, possibly paving the way to prevention and adequate management of disease. We investigated specific hepatic metabolic alterations in mitochondria and oxidative stress during MO at late-gestation. Maternal hepatic tissue was collected at 90% gestation in Control and MO ewes (fed 150% of recommended nutrition starting 60 days before conception). Maternal hepatic redox state, mitochondrial respiratory chain (MRC), and OS markers were investigated. MO decreased MRC complex-II activity and its subunits SDHA and SDHB protein expression, increased complex-I and complex-IV activities despite reduced complex-IV subunit mtCO1 protein expression, and increased ATP synthase ATP5A subunit. Hepatic MO-metabolic remodeling was characterized by decreased adenine nucleotide translocator 1 and 2 (ANT-1/2) and voltage-dependent anion channel (VDAC) protein expression and protein kinase A (PKA) activity (P<0.01), and augmented NAD+/NADH ratio due to reduced NADH levels (P<0.01). MO showed an altered redox state with increased OS, increased lipid peroxidation (P<0.01), decreased GSH/GSSG ratio (P=0.005), increased superoxide dismutase (P=0.03) and decreased catalase (P=0.03) antioxidant enzymatic activities, lower catalase, glutathione peroxidase (GPX)-4 and glutathione reductase protein expression (P<0.05), and increased GPX-1 abundance (P=0.03). MO-related hepatic changes were more evident in the right lobe, corroborated by the integrative data analysis. Hepatic tissue from obese pregnant ewes showed alterations in the redox state, consistent with OS and MRC and metabolism remodeling. These are hallmarks of PALD and hepatic disease, supporting MO as a risk-factor and highlighting OS and mitochondrial dysfunction as mechanisms responsible for liver disease predisposition.

Farnesol prevents aging-related muscle weakness in mice through enhanced farnesylation of Parkin-interacting substrate

Peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) is a master regulator of mitochondrial biogenesis. Reduced PGC-1α abundance is linked to skeletal muscle weakness in aging or pathological conditions, such as neurodegenerative diseases and diabetes; thus, elevating PGC-1α abundance might be a promising strategy to treat muscle aging. Here, we performed high-throughput screening and identified a natural compound, farnesol, as a potent inducer of PGC-1α. Farnesol administration enhanced oxidative muscle capacity and muscle strength, leading to metabolic rejuvenation in aged mice. Moreover, farnesol treatment accelerated the recovery of muscle injury associated with enhanced muscle stem cell function. The protein expression of Parkin-interacting substrate (PARIS/Zfp746), a transcriptional repressor of PGC-1α, was elevated in aged muscles, likely contributing to PGC-1α reduction. The beneficial effect of farnesol on aged muscle was mediated through enhanced PARIS farnesylation, thereby relieving PARIS-mediated PGC-1α suppression. Furthermore, short-term exercise increased PARIS farnesylation in the muscles of young and aged mice, whereas long-term exercise decreased PARIS expression in the muscles of aged mice, leading to the elevation of PGC-1α. Collectively, the current study demonstrated that the PARIS-PGC-1α pathway is linked to muscle aging and that farnesol treatment can restore muscle functionality in aged mice through increased farnesylation of PARIS.

NO-IL-6/10-IL-1β axis: a new pathway in steatotic and non-steatotic liver grafts from brain-dead donor rats

INTRODUCTION

Brain death (BD) and steatosis are both risk factors for organ dysfunction or failure in liver transplantation (LT).

MATERIAL AND METHODS

Here, we examine the role of interleukin 6 (IL- 6) and IL-10 in LT of both non-steatotic and steatotic liver recovered from donors after brain death (DBDs), as well as the molecular signaling pathways underlying the effects of such cytokines.

RESULTS

BD reduced IL-6 levels only in nonsteatotic grafts, and diminished IL-10 levels only in steatotic ones. In both graft types, BD increased IL-1β, which was associated with hepatic inflammation and damage. IL-6 administration reduced IL-1β only in non-steatotic grafts and protected them against damage and inflammation. Concordantly, IL-1β inhibition via treatment with an IL-1 receptor antagonist caused the same benefits in non-steatotic grafts. Treatment with IL-10 decreased IL-1β only in steatotic grafts and reduced injury and inflammation specifically in this graft type. Blockading the IL-1β effects also reduced damage and inflammation in steatotic grafts. Also, blockade of IL-1β action diminished hepatic cAMP in both types of livers, and this was associated with a reduction in liver injury and inflammation, then pointing to IL-1β regulating cAMP generation under LT and BD conditions. Additionally, the involvement of nitric oxide (NO) in the effects of interleukins was evaluated. Pharmacological inhibition of NO in LT from DBDs prompted even more evident reductions of IL-6 or IL-10 in non-steatotic and steatotic grafts, respectively. This exacerbated the already high levels of IL-1β seen in LT from DBDs, causing worse damage and inflammation in both graft types. The administration of NO donors to non-steatotic grafts potentiated the beneficial effects of endogenous NO, since it increased IL-6 levels, and reduced IL-1β, inflammation, and damage. However, treatment with NO donors in steatotic grafts did not modify IL-10 or IL-1β levels, but induced more injurious effects tan the induction of BD alone, characterized by increased nitrotyrosine, lipid peroxidation, inflammation, and hepatic damage.

CONCLUSION

Our study thus highlights the specificity of new signaling pathways in LT from DBDs: NO-IL-6-IL-1β in non-steatotic livers and NO-IL-10-IL-1β in steatotic ones. This opens up new therapeutic targets that could be useful in clinical LT.

Patulin alleviates hepatic lipid accumulation by regulating lipogenesis and mitochondrial respiration

AIMS

The aim of this study is to evaluate the effects of patulin on hepatic lipid metabolism and mitochondrial oxidative function and elucidate the underlying molecular mechanisms.

MAIN METHODS

The effects of patulin on hepatic lipid accumulation were evaluated in free fatty acid-treated AML12 or HepG2 cells through oil red O staining, triglyceride assay, real-time polymerase chain reaction, and western blotting. Alteration of mitochondrial oxidative capacity by patulin treatment was determined using Seahorse analysis to measure the oxygen consumption rate.

KEY FINDINGS

The increased amounts of lipid droplets induced by free fatty acids were significantly reduced by patulin treatment. Patulin markedly activated the CaMKII/AMP-activated protein kinase (AMPK)/proliferator-activated receptor-γ coactivator (PGC)-1α signaling pathway in hepatocytes, reduced the expression of sterol regulatory element binding protein 1c (SREBP-1c) and lipogenic genes, and increased the expression of genes related to mitochondrial fatty acid oxidation. In addition, patulin treatment enhanced the mitochondrial consumption rate and increased the expression of mitochondrial oxidative phosphorylation proteins in HepG2 hepatocytes. The effects of patulin on anti-lipid accumulation; SREBP-1c, PGC-1α, and carnitine palmitoyltransferase 1 expression; and mitochondrial oxidative capacity were significantly prevented by compound C, an AMPK inhibitor.

SIGNIFICANCE

Patulin is a potent inducer of the AMPK pathway, and AMPK-mediated mitochondrial activation is required for the efficacy of patulin to inhibit hepatic lipid accumulation. This study is the first to report that patulin is a promising bioactive compound that prevents the development and worsening of fatty liver diseases, including non-alcoholic fatty liver disease, by improving mitochondrial quality and lipid metabolism.

Peroxisome proliferator-activated receptor γ coactivator 1α maintains NAD+ bioavailability protecting against steatohepatitis

Hepatic metabolic derangements are pivotal incidences in the occurrence of hepatic steatosis, inflammation, and fibrosis. Peroxisome proliferator-activated receptor-γ, coactivator-1α (PGC-1α), a master regulator that mediates adipose metabolism and mitochondrial biogenesis, its role in hepatic steatosis and progression to steatohepatitis remains elusive. By surveying genomic data on nonalcoholic steatohepatitis (NASH) patients available in the Gene Expression Omnibus, we found that PGC-1α was significantly down-regulated compared with healthy controls, implicating the restoration of PGC-1α may ameliorate the hepatopathy. Using a hepatocyte-specific PGC-1α overexpression (LivPGC1α) mouse model, we demonstrated that PGC-1α attenuated hepatic steatosis induced by methionine-choline-deficient diet (MCD). Biochemical measurements and histological examination indicated less inflammatory infiltration, collagen deposition, NF-kB activation, and less lipid accumulation in LivPGC1α liver fed MCD. Further analyses indicated that the NAD+-dependent deacetylase sirtuin 2 (SIRT2) interacted with and deacetylated PGC-1α. Congruently, ablation of SIRT2 accelerated the NASH progression in mice fed MCD, while NAD+ repletion via its precursor mimicked the beneficial effect of PGC-1α overexpression and was sufficient to alleviate NASH in mice. These findings indicate that hepatic-specific overexpression of PGC-1α exerts a beneficial role in the regulation of steatohepatitis and that pharmacological activation of the SIRT2-PGC-1α-NAD+ axis may help to treat NASH.

MTBP and MYC: A Dynamic Duo in Proliferation, Cancer, and Aging

The oncogenic transcription factor c-MYC (MYC) is highly conserved across species and is frequently overexpressed or dysregulated in human cancers. MYC regulates a wide range of critical cellular and oncogenic activities including proliferation, metabolism, metastasis, apoptosis, and differentiation by transcriptionally activating or repressing the expression of a large number of genes. This activity of MYC is not carried out in isolation, instead relying on its association with a myriad of protein cofactors. We determined that MDM Two Binding Protein (MTBP) indirectly binds MYC and is a novel MYC transcriptional cofactor. MTBP promotes MYC-mediated transcriptional activity, proliferation, and cellular transformation by binding in a protein complex with MYC at MYC-bound promoters. This discovery provided critical context for data linking MTBP to aging as well as a rapidly expanding body of evidence demonstrating MTBP is overexpressed in many human malignancies, is often linked to poor patient outcomes, and is necessary for cancer cell survival. As such, MTBP represents a novel and potentially broad reaching oncologic drug target, particularly when MYC is dysregulated. Here we have reviewed the discovery of MTBP and the initial controversy with its function as well as its associations with proliferation, MYC, DNA replication, aging, and human cancer.

Metabolic Dysfunction-associated Fatty Liver Disease (MAFLD) and Viral Hepatitis

A new definition of metabolic dysfunction-associated fatty liver disease (MAFLD) was proposed in 2020. The change from nonalcoholic fatty liver disease (NAFLD) to MAFLD highlights the metabolic abnormalities that accompany fatty liver. The diagnosis of MAFLD does not require exclusion of secondary causes of liver diseases and alcohol consumption. Thus, MAFLD may coexist with other types of liver diseases, such as viral hepatitis, a disease that remains the most common cause of liver disease-related death. With the increasing prevalence of MAFLD, patients with coincidental MAFLD and viral hepatitis are frequently encountered in clinical practice. In this review, we mainly summarize the mutual relationship between hepatitis B/C and systematic metabolism dysfunction related to MAFLD. We discuss the impact of MAFLD on progression of viral hepatitis and the therapies. Some unaddressed clinical problems related to concomitant MAFLD and viral hepatitis are also identified.

The Symbiotic Effect of a New Nutraceutical with Yeast β-Glucan, Prebiotics, Minerals, and Silybum marianum (Silymarin) for Recovering Metabolic Homeostasis via Pgc-1α, Il-6, and Il-10 Gene Expression in a Type-2 Diabetes Obesity Model

The use of natural products and derivatives for the prevention and control of non-communicable chronic diseases, such as type-2 diabetes (T2D), obesity, and hepatic steatosis is a way to achieve homeostasis through different metabolic pathways. Thus, male C57BL/6 mice were divided into the following groups: high-fat diet (HFD) vehicle, HFD + Supplemented, HFD + Supplemented_S, and isolated compounds. The vehicle and experimental formulations were administered orally by gavage once a day over the four weeks of the diet (28 consecutive days). We evaluated the energy homeostasis, cytokines, and mitochondrial gene expression in these groups of mice. After four weeks of supplementation, only the new nutraceutical group (HFD + Supplemented) experienced reduced fasting glycemia, insulin, HOMA index, HOMA-β, dyslipidemia, ectopic fat deposition, and hepatic fibrosis levels. Additionally, the PPARγ coactivator 1 α (Pgc-1α), interleukin-6 (Il-6), and interleukin-10 (Il-10) gene expression were augmented, while hepatic steatosis decreased and liver parenchyma was recovered. The glutathione-S-transferase activity status was found to be modulated by the supplement. We discovered that the new nutraceutical was able to improve insulin resistance and hepatic steatosis mainly by regulating IL-6, IL-10, and Pgc-1α gene expression.

The anti-inflammatory effects of Akkermansia muciniphila and its derivates in HFD/CCL4-induced murine model of liver injury

Inflammation plays a critical role in the promotion of hepatocyte damage and liver fibrosis. In recent years the protective role of Akkermansia muciniphila, a next-generation beneficial microbe, has been suggested for metabolic and inflammatory disorders. In this study, we aimed to evaluate the effects of live and pasteurized A. muciniphila and its extra cellular vesicles (EVs) on inflammatory markers involved in liver fibrosis in a mouse model of a high-fat diet (HFD)/carbon tetrachloride (CCl₄)-induced liver injury. Firstly, the responses of hepatic stellate cells (HSCs) to live and pasteurized A. muciniphila and its EVs were examined in the quiescent and LPS-activated LX-2 cells. Next, the anti-inflammatory effects of different forms of A. muciniphila were examined in the mouse model of HFD/CCl₄-induced liver injury. The gene expression of various inflammatory markers was evaluated in liver, colon, and white adipose tissues. The cytokine secretion in the liver and white adipose tissues was also measured by ELISA. The results showed that administration of live and pasteurized A. muciniphila and its EVs leads to amelioration in HSCs activation. Based on data obtained from the histopathological analysis, an improvement in gut health was observed through enhancing the epithelium and mucosal layer thickness and strengthening the intestinal integrity in all treatments. Moreover, live A. muciniphila and its EVs had inhibitory effects on liver inflammation and hepatocytes damage. In addition, the tissue cytokine production and inflammatory gene expression levels revealed that live A. muciniphila and its EVs had more pronounced anti-inflammatory effects on liver and adipose tissues. Furthermore, EVs had better effects on the modulation of gene expression related to TLRs, PPARs, and immune response in the liver. In conclusion, the present results showed that oral administration of A. muciniphila and its derivatives for four weeks could enhance the intestinal integrity and anti-inflammatory responses of the colon, adipose, and liver tissues and subsequently prevent liver injury in HFD/CCL₄ mice.

Linagliptin ameliorates acetic acid-induced colitis via modulating AMPK/SIRT1/PGC-1α and JAK2/STAT3 signaling pathway in rats

Ulcerative colitis is a chronic inflammatory disease, profoundly affecting the patient's quality of life and is associated with various complications. Linagliptin, a potent DPP- IV inhibitor, shows favorable anti-inflammatory effects in several animal model pathologies. To this end, the present study aimed to investigate the anti-inflammatory effect of linagliptin in a rat model of acetic acid-induced colitis. Moreover, the molecular mechanisms behind this effect were addressed. Accordingly, colitis was established by the administration of a 2 ml 6% acetic acid intrarectally and treatment with linagliptin (5 mg/kg) started 24 h after colitis induction and continued for 7 days. On one hand, the DPP-IV inhibitor alleviated the severity of colitis as evidenced by a decrease of disease activity index (DAI) scores, colon weight/length ratio, macroscopic damage, and histopathological deteriorations. Additionally, linagliptin diminished colon inflammation via attenuation of TNF-α, IL-6, and NF-κB p65 besides restoration of anti-inflammatory cytokine IL-10. On the other hand, linagliptin increased levels of p-AMPK, SIRT1, and PGC-1α while abolishing the increment in p-JAK2 and p-STAT3. In parallel linagliptin reduced mTOR levels and upregulated expression levels of SHP and MKP-1 which is postulated to mediate AMPK-driven JAK2/STAT3 inhibition. Based on these findings, linagliptin showed promising anti-inflammatory activity against acetic acid-induced colitis that is mainly attributed to the activation of the AMPK-SIRT1-PGC-1α pathway as well as suppression of the JAK2/STAT3 signaling pathway that might be partly mediated through AMPK activation.

Nonalcoholic fatty liver disease or metabolic dysfunction-associated fatty liver disease diagnoses and cardiovascular diseases: From epidemiology to drug approaches

BACKGROUND

A consensus of experts has proposed to replace the term nonalcoholic fatty liver disease (NAFLD), whose global prevalence is 25%, with metabolic dysfunction-associated fatty liver disease (MAFLD), to describe more appropriately the liver disease related to metabolic derangements. MAFLD is closely intertwined with type 2 diabetes, obesity, dyslipidaemia, all linked to a rise in the risk of cardiovascular disease (CVDs). Since controversy still stands on whether or not NAFLD/MAFLD raises the odds of CVD, the present review aims to evaluate the impact of NAFLD/MAFLD aetiologies on CV health and the potential correction by dietary and drug approaches.

RESULTS

Epidemiological studies indicate that NAFLD raises risk of fatal or non-fatal CVD events. NAFLD patients have a higher prevalence of arterial plaques and stiffness, coronary calcification, and endothelial dysfunction. Although genetic and environmental factors strongly contribute to NAFLD pathogenesis, a Mendelian randomization analysis indicated that the PNPLA3 genetic variant leading to NAFLD may not be causally associated with CVD risk. Among other genetic variants related to NAFLD, TM6SF2 appears to be protective, whereas MBOAT7 may favour venous thromboembolism.

CONCLUSIONS

NAFLD is correlated to a higher CVD risk which may be ameliorated by dietary interventions. This is not surprising, since new criteria defining MAFLD include other metabolic risk abnormalities fuelling development of serious adverse extrahepatic outcomes, for example CVD. The present lack of a targeted pharmacological approach makes the identification of patients with liver disease at higher CVD risk (eg diabetes, hypertension, obesity or high levels of C-reactive protein) of major clinical interest.

5-Aminolevulinic acid combined with sodium ferrous citrate (5-ALA/SFC) ameliorated liver injury in a murine acute graft-versus-host disease model by reducing inflammation responses through PGC1-α activation

Acute graft-versus-host disease (aGvHD) remains lethal as a life-threatening complication after allogeneic hematopoietic stem cell transplantation (HSCT). Inflammatory responses play an important role in aGvHD. 5-Aminolevulinic acid combined with sodium ferrous citrate (5-ALA/SFC) has been widely reported to have a major effect on the anti-inflammatory response; however, these effects in aGvHD models have never been reported. In this study, a murine aGvHD model was developed by transferring spleen cells from donor B6/N (H-2kb) mice into recipient B6D2F1 (H-2kb/d) mice. In addition to evaluating manifestations in aGvHD mice, we analyzed the serum ALT/AST levels, liver pathological changes, infiltrating cells and mRNA expression of inflammation-related cytokines and chemokines. 5-ALA/SFC treatment significantly ameliorated liver injury due to aGvHD and decreased the population of liver-infiltrating T cells, resulting in a reduced expression of pro-inflammatory cytokines and chemokines. Furthermore, the mRNA expression proliferator-activated receptor-γcoactivator (PGC-1α) was enhanced, which might explain why 5-ALA/SFC treatment downregulates inflammatory signaling pathways. Our results indicated that 5-ALA/SFC can ameliorate liver injury induced by aGvHD through the activation of PGC-1α and modulation of the liver mRNA expression of inflammatory-related cytokines and chemokines. This may be a novel strategy for treating this disease.